1. Field of the Invention:
This invention relates to a method for photographing original images recorded on a document of varying form and additional information relevant thereto on a microfilm and an apparatus used therefor.
2. Description of the related Art:
On microfilm on which original images recorded in a document of varying nature are photographed, information of a varying sort that is useful for retrieval of the photographed images is additionally photographed for the purpose of facilitating management and retrieval of the photographed images. As the additional information for retrieval are counted document marks otherwise called blip marks are well known, which marks are used for counting image frames and, at the same time, discerning image sizes. As another sort of information for retrieval, a series of frame numbers representing serial numbers assigned to the individual images are photographed on the microfilm.
As method of additionally photographing such information for retrieval as mentioned above on the film, known methods include one which comprises forming on a document stand a display part for displaying the information for retrieval in a position within the coverage of microfilm (field of view of the camera) on the document stand and allowing the additional information for retrieval to be photographed on the microfilm simultaneously with the original image from the document and another which comprises incorporating such a display part in the camera head thereby permitting simultaneous photographing of the original image and the relevant information for retrieval on the microfilm.
FIG. 10 is a diagram illustrating a microfilm camera which embodies the former method. This camera comprises a base table 1 for supporting a document, a supporting pole 2 fixed on the base table 1, a camera head 3 attached to the supporting pole 2 and adapted to photograph an original image recorded on the document on a microfilm, and illuminators 4 for illuminating the base table 1. On the base table 1, a display part 5 for displaying the document marks mentioned above and a display part 6 for displaying the frame numbers mentioned above are so disposed in the proximity of the document as to be located within the field of view of a lens 7 attached to the camera head 3. A microfilm camera embodying the latter method is disclosed in U.S. Pat. No. 4,701,046, for example.
When the display part for photographing the information for retrieval is installed on the base table as described above, the exposure time is varied by the contrast among the original images recorded on the document and the images of information for retrieval are consequently photographed in inconsistent density. This inconsistency of density not only prevents the photographed microfilm from acquiring fine quality but also constitutes itself a possible cause for an erroneous operation during the course of retrieval in an extreme case. When the ratio of magnification of the optical system is varied by the size of document or the size of film, the size of the images of information photographed on the microfilm is consequently varied. To avoid this drawback the size of numerals and other similar figures on the display part used in representing the information for retrieval must be varied proportionately to the ratio of magnification.
When the photographing of the information for retrieval is to be effected within the camera head as described above, an idea of enabling the original images of the document to be photographed simultaneously with the information for retrieval is not easily materialized because the head interior has a limited space. The solution of this difficulty has no alternative but to rely on a method which comprises first photographing an original image of the document, then advancing the microfilm to the next frame, and thereafter photographing the information for retrieval of the photographed image. In this method, however, when the original images recorded on the document have a plurality of sizes such as single size and double size, for example, the amounts of advance of the microfilm are varied with the sizes of original images. Thus, the positions of the microfilm at which the images of information for retrieval are photographed on the microfilm must be changed by the sizes of original images.
Further, in the case of the conventional microfilm camera disclosed in the U.S. Pat. specification, the photographing of a document mark among the information for retrieval is effected by selectively spotting light upon a display part bearing the numeral corresponding to the kind of mark to be photographed and the photographing of the relevant frame number is attained by a display part bearing the numeral corresponding to the largest number of digits of the numeral mentioned above. In other words, the information for retrieval is simultaneously photographed on the microfilm, with the document mark in a prescribed width and the numeral in a prescribed numer of digits. The display part used therefor is relatively large and, as the result, the optical system for photographing the information for retrieval is proportionately large. As a consequence, the cost of the entire system is inevitably increased and the camera head unduly gains in size and complexity.